This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Chronic Kidney Disease in Children (CKiD) study is a prospective cohort enrolling 540 children between January 2005 and December 2006, which is sponsored by the US National Institutes of Health (i.e., NIDDK, NINDA, NICHD and NLHBI). Eligible children are aged 1 to 16 years with an estimated glomerular filtration rate (GFR) between 30 and 75 ml/min|1.73m2 via the Schwartz formula at study entry;CKiD will exclude children who have had organ or stem cell transplantation;cancer/leukemia treatment, HIV treatment, or pregnancy within the past year;dialysis within the past 3 months;or a previous diagnosis of structural heart disease or a genetic syndrome involving the central nervous system (e.g., Downs syndrome). Annual study visits consist of physician examination, collection of blood and urine samples, and questionnaires eliciting information on quality of life, demographics, and medical and family histories. At alternating annual study visits, children further undertake (a) GFR estimated by Iohexol plasma disappearance curves, echocardiogram, and 24-hour ambulatory blood pressure monitoring, or (b) neurocognitive screening and additional biological specimens to quantify growth. Primary goals are to determine (1) the risk factors for decline in renal function;(2) the incidence of, and risk factors for, impaired neurocognitive development;(3) the prevalence of risk factors for cardiovascular disease;and (4) the long-term effects of growth failure and its treatment. The primary outcome is the rate of decline in GFR;a secondary outcome is time-to-ESRD, defined by transplantation, dialysis, or a 50% decline in GFR. With a two-sided type I error rate of 5%, CKiD is designed to have 80% statistical power to detect a 1.25-fold ratio of the slope of GFR in 208 exposed children to 312 unexposed children, allowing for attrition of 10%, 5% and 5% over the first 3 years of follow up, a dependence among the repeated measurements of GFR within children, and an overall annual decline in GFR of 5 ml/min|1.73m2 (study website: www.statepi.jhsph.edu).